The invention relates to a diaphragm valve, having a valve housing and at least one valve member movable relative to this housing, wherein the valve member has a diaphragm carrier movable relative to the valve housing through the execution of a switchover movement and also a flexible sealing diaphragm which, together with the valve housing, bounds a valve chamber, wherein the sealing diaphragm is fixed to the valve housing under sealing at its outer edge section and has a mounting diaphragm section fastened to the diaphragm carrier with clearance from said outer edge section and accompanying the switchover movement, wherein there is mounted in the valve chamber a valve seat facing the sealing diaphragm, against which a sealing section of the sealing diaphragm at least partly supported by a base surface of the diaphragm carrier facing the valve chamber may be pressed with sealing, in order to separate from one another two fluid passages opening into the valve chamber.
A diaphragm valve of this type known from EP 1 722 137 A2 contains at least one valve member, mounted in a valve housing and comprising a sealing diaphragm bounding a valve chamber, and a diaphragm carrier which carries the sealing diaphragm and is designed in the manner of a plunger and may be moved linearly relative to the valve housing. The diaphragm carrier supports with its base surface an annular sealing section of the sealing diaphragm which may be brought into contact with an annular valve seat located in the valve chamber, so as to separate from one another two fluid passages opening into the valve chamber. The sealing section is part of a diaphragm section fixed to the valve member and which may be described as the mounting diaphragm section and which accompanies the switchover movement of the diaphragm carrier. At its outer edge section the sealing diaphragm is clamped with sealing to the valve housing. A disadvantage of the known diaphragm valve lies in the fact that, during switchover of the valve member, the sealing diaphragm is for a time heavily stretched and therefore subject to great stress, which may have a disadvantageous effect on its service life.
Known from DE 20023225 U1 is a diaphragm valve of similar design, which has two valve members, each containing a diaphragm carrier designed in the manner of a plunger, and a sealing diaphragm fastened to the diaphragm carrier and cooperating with a valve seat, wherein the sealing diaphragms may be made in one piece with a diaphragm body.
DE 60017310 T2 discloses a diaphragm valve with a valve housing with a diaphragm carrier carrying a sealing diaphragm and suspended from a valve housing. With its base surface the diaphragm carrier supports two sealing sections of the sealing diaphragm, each able to cooperate with a separate valve seat in order to connect with or separate from one another altogether three fluid passages opening into a valve chamber. The switching position of the valve carrier may be preset by drive means which act on the diaphragm carrier and generate its pivoting switchover movement. With this diaphragm valve too there is the problem that the flexible sealing diaphragm, especially in the diaphragm section extending between the diaphragm carrier and the fixed edge section, is heavily stretched and subject to high tensile stresses.
In the case of a diaphragm valve known from DE 20 2009 016 447 U1, a sealing diaphragm is fastened to a pivotable diaphragm carrier only in the area of two sealing sections, each opposite a valve seat. The problems of a sealing diaphragm which is heavily stressed on account of its being stretched also apply to this diaphragm valve. The same applies to the diaphragm valve described in DE 20 2009 000 593 U1, in which the diaphragm valve is pivotable in the manner of a rocker, in order to change the switching position of the valve.
A diaphragm valve known from DE 7324333 U has a sealing diaphragm which seals a valve chamber and which is held tight by a stiffening plate. Projections extending away from the sealing diaphragm pass through the stiffening plate and rest on an actuating element mounted pivotably independent of the sealing diaphragm in a valve housing. The sealing diaphragm does not take part in the pivoting movement of the diaphragm carrier, which impairs the available valve stroke.
FR 2795798 A discloses a diaphragm valve with a valve member which has a pivotable diaphragm carrier and a diaphragm body fastened to the diaphragm carrier, wherein the diaphragm body forms a sealing diaphragm, fixed in the valve housing at the edge with sealing. In pivoting of the diaphragm carrier, a diaphragm section of the sealing diaphragm bordering the diaphragm carrier is subject to high tensile stress, which can impair life expectancy.
Further types of diaphragm valve are known from U.S. Pat. No. 6,789,781 B2, WO 2004/005778 A1, GB 596533 A, DE 102005021583 A1 and U.S. Pat. No. 7,779,867 B2.